Windows including glass substrates with solar control coatings provided thereon are known in the art. Such windows may be used in the context of architectural windows, insulating glass (IG) window units, automotive windows, and/or the like.
U.S. Pat. No. 5,514,476 discloses a coated article having a layer stack of glass/SiN/NiCr/Ag/NiCr/SiN, where SiN stands for silicon nitride. While such coatings are certainly good overall coatings usable in applications such as windshields and architectural windows, they tend to be problematic in certain respects. For example, while such layer stacks with NiCr contact layers (a “contact layer” is a layer which contacts an IR reflecting layer such as silver) provide efficient solar control and are overall good coatings, the NiCr layers are lacking in terms of: (a) corrosion resistance to acid (e.g., HCl boil); and/or (b) mechanical performance such as scratch resistance.
It is also known in the art to use niobium (Nb) as a material for contact layers. For example, U.S. Pat. No. 6,355,334 discloses the use of Nb as a contact layer to be provided immediately above a silver layer. U.S. Pat. No. 6,045,896 also discloses the use of Nb as a contact layer immediately above a silver layer. Unfortunately, Nb layers are also lacking with respect to chemical durability. In particular, Nb suffers damage when exposed to certain chemicals such as alkaline solutions, e.g., upon exposure to a one hour NaOH boil test for measuring durability. In commercial use, pinholes can form in the outer dielectric layer(s) thereby exposing the contact layer(s) in certain areas; and if it is damaged by alkaline solutions this can lead to durability issues and coating failure. For example, certain photographs in U.S. patent application Ser. No. 10/370,060, filed Feb. 21, 2003 (hereby incorporated herein by reference) illustrate that Nb layers are often damaged by the one hour NaOH boil test (one hour boil in solution including about 0.1 normal NaOH solution—0.4% NaOH mixed with water—at about 195 degrees F.). For the boil test, see ASTM D 1308-87, incorporated herein by reference.
Accordingly, there exists a need in the art for a coated article that has improved durability. A non-limiting example of improved durability is improved resistance to alkaline solutions thereby indicating improved chemical durability. It is an example purpose of certain embodiments of this invention to fulfill this need, and/or other needs which will become apparent to the skilled artisan once given the following disclosure.